From 91a30b70cedef704962ad428112da61a3f3b024d Mon Sep 17 00:00:00 2001 Message-Id: <91a30b70cedef704962ad428112da61a3f3b024d.1342518105.git.minovotn@redhat.com> In-Reply-To: <27a73856ecc481c66c7afac8171f753887f32e31.1342518105.git.minovotn@redhat.com> References: <27a73856ecc481c66c7afac8171f753887f32e31.1342518105.git.minovotn@redhat.com> From: Luiz Capitulino Date: Tue, 5 Jun 2012 14:58:42 +0200 Subject: [PATCH 33/41] qemu-ga: become_daemon(): reopen standard fds to /dev/null RH-Author: Luiz Capitulino Message-id: <1338908331-15633-28-git-send-email-lcapitulino@redhat.com> Patchwork-id: 39925 O-Subject: [PATCH RHEL6.4 qemu-kvm 27/36] qemu-ga: become_daemon(): reopen standard fds to /dev/null Bugzilla: 827612 RH-Acked-by: Paolo Bonzini RH-Acked-by: Juan Quintela RH-Acked-by: Jeffrey Cody This fixes a bug where qemu-ga doesn't suspend the guest because it fails to detect suspend support even when the guest does support suspend. This happens because of the way qemu-ga fds are managed in daemon mode. When starting qemu-ga with --daemon, become_daemon() will close all standard fds. This will cause qemu-ga to end up with the following fds (if started with 'qemu-ga --daemon'): 0 -> /dev/vport0p1 3 -> /run/qemu-ga.pid Then a guest-suspend-* function is issued. They call bios_supports_mode(), which will call pipe(), and qemu-ga's fd will be: 0 -> /dev/vport0p1 1 -> pipe:[16247] 2 -> pipe:[16247] 3 -> /run/qemu-ga.pid bios_supports_mode() forks off a child and blocks waiting for the child to write something to the pipe. The child, however, closes its reading end of the pipe _and_ reopen all standard fds to /dev/null. This will cause the child's fds to be: 0 -> /dev/null 1 -> /dev/null 2 -> /dev/null 3 -> /run/qemu-ga.pid In other words, the child's writing end of the pipe is now /dev/null. It writes there and exits. The parent process (blocked on read()) will get an EOF and interpret this as "something unexpected happened in the child, let's assume the guest doesn't support suspend". And suspend will fail. To solve this problem we have to reopen standard fds to /dev/null in become_daemon(), instead of closing them. Signed-off-by: Luiz Capitulino Reviewed-by: Eric Blake Signed-off-by: Michael Roth (cherry picked from commit 226a48949cf74006a94b5931e50352b2af801ac7) Signed-off-by: Luiz Capitulino --- qemu-ga.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) Signed-off-by: Michal Novotny --- qemu-ga.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/qemu-ga.c b/qemu-ga.c index 8d53e04..6e7caed 100644 --- a/qemu-ga.c +++ b/qemu-ga.c @@ -445,9 +445,9 @@ static void become_daemon(const char *pidfile) goto fail; } - close(STDIN_FILENO); - close(STDOUT_FILENO); - close(STDERR_FILENO); + reopen_fd_to_null(STDIN_FILENO); + reopen_fd_to_null(STDOUT_FILENO); + reopen_fd_to_null(STDERR_FILENO); return; fail: -- 1.7.10.4